Not only compact cameras and cameras for mobile devices but also mirrorless cameras and single-lens reflex cameras have a tendency to be gradually miniaturized. Accordingly, development of a thin type optical system for a small camera has been demanded. Recently, a cata-dioptric system has been developed, which implements thin shaping with performing of focusing utilizing both a reflective optical system and a refractive optical system.
A reflective lens is configured so that light is transferred through multiple reflections and the transferred light forms an image. However, it is necessary for such a reflective lens to have a configuration for blocking stray light if the stray light, other than a field of view, is incident. The stray light means an undesirable noise light that occurs due to a cause other than normal refraction or reflection.
Accordingly, there is a need for a cata-dioptric system that can implement thin shaping of an optical system with proper blocking of stray light.